vacuum secondary question

[Aussie FJ40]

ave just installed a fully rebuilt 2f out of a 84 fj60 and it appears to be starving does the vacuum secondary work when you give it full throttle through the gears? i have not had an original carb before only a holley and other than a new diaphragm to be fitted(waiting for it) everything checks out fine , im thinking i should feel it come in,would that be a fair call?it is just not going as hard as the old engine did with the holley and i was execting it to be heaps better,thanks

 

[subzali]

I believe the mechanical secondary in the earlier 2bbl Aisan carbs gives more of a "kick" under hard acceleration. The vacuum-actuated secondary is a little more subtle. You should stick a paperclip on the actuating rod to make sure that it's actuating.

Like this before:

After:

Also make sure you have full movement of your throttle linkage, and make sure your bushing is in good shape.

Like this:

Not like this:

I don't think the Aisan is advertised to have as much "get-up-and-go" response as a Holley, but it should net you more better fuel economy and better off-road performance (e.g. not flooding).

Oh, there's also an orifice in the vacuum circuit that causes a delay in the secondaries opening up. So you may or may not get the paperclip to move until you've been able to sustain WOT for more than a couple seconds...

 

[SteveH]

Matt is correct on this - The secondaries do not kick in with some notable feel - it takes some time on the throttle to get them to open. The paperclip test is the only way I know of to be sure they are opening.

Matt - do you know what year the carb went from mechanically-actuated secondaries to vacuum-actuated?

 

[subzali]

I believe the vacuum secondary started with the 2F - so 1975.

 

[CruiserStuff]

Great responses, guys.......

 

[FJsnoozer]

wow, This is extremely helpful. I had never heard it, and with the top off and quiet exhaust, I had not heard a "hit" like I am used to on the old 4 barrel 302s I drove.

 

[Aussie FJ40]

thanks for the input i will try the clip method, should have the new diaphragm today, maybe its a case of quiet engine(rebuilt) 5speed etc and not used to it,thanks again,Baz